1. Field of the Invention
The present invention relates to magnetic powder for validity determining ink, a manufacturing method for magnetic powder for validity determining ink, magnetic ink for validity determination, a printing member for validity determination, a detecting device for the printing member for validity determination, and a validity determining device which are applied to printing of, for example, health insurance cards and ID cards having intrinsic numbers respectively, Shinkansen reserved tickets issued by travel agencies and ticket centers, tickets having the value printed on specific forms such as concert tickets, and securities such as bank tickets, bills, stocks, and gift certificates.
2. Description of the Related Art
Forgery preventive measures for notes as money, securities, and cards having the value equal to cash are taken. Particularly, an art for printing a certain kind of information on a paper sheet with magnetized ink and magnetically detecting the information is easy in recording and erasing information and used widely. Further, recently, for example, as disclosed in U.S. Pat. No. 5,533,759 (Jeffers, Jul. 9, 1996), an objective document is printed using magnetic ink including a magnetic pigment having a Curie temperature lower than 130xc2x0 C. and the printed part is magnetized in an optional magnetic pattern. The magnetized part is heated at least up to 130xc2x0 C. using a heat lamp. The validity of the document is determined depending on whether the magnetic pattern is destroyed by heat in the temperature region beyond the Curie point or not. However, in U.S. Pat. No. 5,533,759 mentioned above, the particle diameter of the magnetic pigment included in the magnetic ink is not disclosed. When the particle diameter of the magnetic pigment is larger than a predetermined value, the magnetic pigment cannot respond sufficiently to the high resolution like printing by an ink jet printer. Further, when the particle diameter of the magnetic pigment is larger than a predetermined value and the magnetic pigment is printed on a paper sheet, particularly the magnetic information recorded on the surface is gradually torn off due to friction with the magnetic detection head during reading and it is anxious that the SN ratio may be reduced during reading of the information.
On the other hand, as input-output devices such as scanners, printers, and copying machines, personal computers, and image processing software have been highly advanced recently, even devices on sale can commit highly precise forge. In order to respond to this situation, various forgery preventive arts are applied to securities and individual authentication ID cards. Particularly, from the viewpoint of that information is invisible to a human, arts using a magnetic material are widely used. For example, in securities, an art for printing a predetermined area with magnetic ink with magnetic powder mixed and determining the validity by detecting the existence of magnetism or the magnetic pattern itself is known. Further, in IC cards, it is known to magnetically record information on a magnetic stripe, reproduce it, and authenticate an individual.
As mentioned above, generally, output detection by magnetism can respond to determination of the validity by high-speed reading comparatively easily, so that it has been used in various fields. However, the conventional method determines the validity depending on judgment of whether there is magnetic information in a predetermined position or not, so that using a material of Fe3O4 or others which can be obtained comparatively easily, forging arts using the latest printing art are generated frequently.
In the aforementioned magnetic forgery preventive art, a recording and reproducing apparatus can be prepared comparatively simply and can read recorded information easily, so that an art having weak resisting force to forgery and a high security property is required.
An object of the present invention is to obtain magnetic powder for validity determining ink which is satisfactory in output and durability, applicable to various printing arts, and high in the reliability, determining speed, and forgery preventive effect.
Another object of the present invention is to provide a manufacturing method for magnetic powder for validity determining ink which is satisfactory in the durability, applicable to various printing arts, high in the reliability, determining speed, and forgery preventive effect, and easily capable of obtaining a desired particle diameter.
Furthermore, still another object of the present invention is to provide magnetic ink for validity determination that is satisfactory in the durability, applicable to various printing arts, and high in the reliability, determining speed, and forgery preventive effect.
A further object of the present invention is to provide a printing member for validity determination that is satisfactory in the durability and high in the reliability, determining speed, and forgery preventive effect.
A still further object of the present invention is to provide a detecting device for a printing member for validity determination that is high in the reliability, determining speed, and forgery preventive effect.
Yet a further object of the present invention is to provide a validity-determining device for a printing member for validity determination that is high in the reliability, determining speed, and forgery preventive effect.
According to the present invention, magnetic powder for validity determining ink comprising magnetic oxide powder having a Curie temperature between xe2x88x9250xc2x0 C. and 150xc2x0 C. and a mean powder particle diameter of 10 xcexcm or less is provided.
Furthermore, according to the present invention, a manufacturing method for magnetic powder for validity determining ink is provided and the manufacturing method comprises the steps of dissolving a magnetic oxide and a glass forming material to obtain a mixture thereof; cooling the mixture rapidly to make the amorphous magnetic oxide; heat-treating the amorphous mixture to crystallize the magnetic oxide; and removing the glass forming material from the crystallized mixture to obtain magnetic oxide powder having a mean crystal particle diameter of 10 xcexcm or less.
Further, according to the present invention, magnetic ink for validity determination including first magnetic powder having a first Curie temperature between xe2x88x9250xc2x0 C. and 150xc2x0 C. and a mean powder particle diameter of 10 xcexcm or less is provided.
Furthermore, according to the present invention, a printing member for validity determination is provided and the printing member for validity determination comprises a base; a first magnetic image printed on the base with the first magnetic ink including first magnetic powder having a first Curie temperature; and a second magnetic image printed on the base with second magnetic ink including second magnetic powder having a second Curie temperature higher than that of the first magnetic powder.
Further, according to the present invention, a detecting device for a printing member for validity determination is provided and the detecting device comprises means for conveying a printing member for validity determination having the first magnetic image printed with the first magnetic ink including the first magnetic powder having the first Curie temperature and the second magnetic image printed with the second magnetic ink including the second magnetic powder having the second Curie temperature higher than that of the first magnetic powder; a heater for heating the printing member for validity determination to a temperature higher than the first Curie temperature and lower than the second Curie temperature; and magnetic characteristic detecting means for detecting magnetic characteristics from the heated printing member for validity determination.
Furthermore, according to the present invention, a validity determining device is provided and the validity determining device comprises means for conveying a printing member for validity determination having the first magnetic image printed with the first magnetic ink including the first magnetic powder having the first Curie temperature and the second magnetic image printed with the second magnetic ink including the second magnetic powder having the second Curie temperature higher than that of the first magnetic powder; a heater for heating the printing member for validity determination to a temperature higher than the fist Curie temperature and lower than the second Curie temperature; a first magnetic detecting section installed at the preceding stage of the heater for detecting magnetic characteristics from the printing member for validity determination; a second magnetic detecting section installed at the later stage of the heater for detecting magnetic characteristics from the printing member for validity determination; and a validity determining section for determining the validity of the printing member for validity determination from a first detected magnetic pattern detected by the first magnetic detecting section and a second detected magnetic pattern detected by the second magnetic detecting section.